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While excitonic semiconductors offer appealing optical properties, their application for competitive optoelectronic devices has remained limited. Here, the authors report the realization of broadband exciton-polariton photodiodes based on a layered excitonic semiconductor, WS₂, contacted by tin-doped indium oxide in an open optical cavity design, showing ~MHz bandwidth at room temperature.

Here, the authors report a study of the infrared optoelectronic properties of twisted 2D black phosphorus (BP), showing photoluminescence emission from optical transitions that are symmetry-forbidden in BP and spontaneous electronic polarization generating interfacial bulk photovoltaic effect.

Nonlinear optical effects in 2D materials can be used for neuromorphic computing systems. Here, the authors introduced free-space optical computing within a bare MoS₂ array. Neural network and digital processing were demonstrated, showing fast speed, low energy consumption, and high signal-to-noise ratio.

A neuromorphic photovoltaic detector with highly tunable responsivity and simultaneous non-volatile storage of image data has been demonstrated in a neural network, representing a transformative leap in the compactness and function of visual perception hardware.

Neuromorphic motion devices improve dynamic tracking but are generally limited to near-infrared. Here, the authors use PdSe₂/pentacene heterostructures to develop a neuromorphic transistor for efficient mid-infrared real-time motion trajectory memorization and flame direction classification.

The avalanche or carrier-multiplication effect has the potential to improve the performance of photodetectors and solar cells, but usually requires high threshold energies. Here, the authors report stepwise WSe₂ homojunctions exhibiting threshold energies approaching the semiconductor bandgap at room temperature.

The intrinsic photovoltaic effect (IPVE) in noncentrosymmetric materials has the potential to overcome the limitations of traditional photovoltaic devices. Here, the authors report the observation of a strong and gate-tunable IPVE in 1D grain boundaries of a van der Waals semiconductor, ReS₂.

Gate-tunable heterojunction diodes—or triodes—that are based on van der Waals heterostructures formed from two-dimensional indium selenide and three-dimensional silicon can exhibit subthreshold slopes of 6.4 mV decade^–1 and on-state current densities of 0.3 µA µm^–1 at a drain bias of –1 V.

Band-engineered van der Waals heterostructures that block dark current without suppressing photocurrent can be used to build detectors with high room-temperature detectivity for visible light and blackbody infrared light.

Photovoltaic devices based on 2D materials still suffer from low quantum efficiencies due to interfacial charge recombination and inefficient contacts. Here, the authors design photovoltaic detectors and photodiodes based on MoS₂ and doped AsP heterojunction with unilateral depletion region reporting high external quantum efficiency of 71% under zero applied bias.

The authors investigate the optical properties of a heterostructure formed by a metallic substrate and a nanostructured transition metal dichalcogenide multilayer by measuring the reflectance spectrum at different multilayer thicknesses, filling factors and grating periods. The spectra show strong dispersion and avoided crossing of excitons, plasmons and cavity photons along with excitonic mode suppression at the anti-crossing point.

Critical band-to-band tunneling is demonstrated at the van der Waals interface, with potential applications in optoelectronic memory.

Multi-functional integration! The memristor integrates four functions of multi-level storage, logic gates, UV sensing, and neuromorphic computing in one device.

Two-terminal artificial optoelectronic devices in which photoexcited carriers and ions are coupled constitute a built-in artificial neural network that can sense, memory and process simultaneously.